TravisCI build for OS X fails constantly

[nkryuchkov]

Describe the bug
TravisCI builds for OS X fail constantly after executing Compiling @ngx-translate/core : es2015 as esm2015 in make lint-ui.

Environment information:

• TravisCI, OSX

Steps to Reproduce
Steps to reproduce the behavior:

1. Do anything that makes TravisCI create a build.

Actual behavior
Build fails.

Expected behavior
Build succeeds.

Additional context
I don't remember this error before the recent update of Angular. But I may be wrong here. The issue might be related to the update or to the ngx-translate/core dependency.

Possible implementation
@Senyoret1 had an idea of updating ngx-translate/core to the latest version.

[Senyoret1]

After some testing, the problem turned out to be because Travis is using MacOS 10.11. If you change osx_image: xcode8 to osx_image: xcode8.3 in the .travis.yml file it works

[nkryuchkov]

@Senyoret1 Thanks. Let's try that.

[nkryuchkov]

@Senyoret1 That fixed the issue. Great.